Direct liquid refrigerant supply and return system

ABSTRACT

A refrigerant system in which liquid halocarbon compound refrigerant is delivered at pressures in excess of evaporation pressure through metering outlets in a supply header of an evaporator in a manner to provide uniform cooling throughout the evaporator and utilizing a return header and liquid-vapor lift apparatus to return vaporized and unevaporated refrigerant to an accumulator-separator of the refrigeration system.

United States Patent Garland et al.

DIRECT LIQUID REFRIGERANT SUPPLY AND RETURN SYSTEM Inventors: Milton W.Garland, Waynesboro,

Pa.; Robert C. Fish, St. Louis, Mo.

Assignee: Frick Company, Waynesboro, Pa.

Filed: May 6, 1974 Appl. No.: 467,318

Related US. Application Data Continuation-in-part of Ser. No. 352,814,April 19, 1973, abandoned.

US. Cl. 62/498; 62/221; 62/235; 62/525; 62/527; 165/174; 165/175 Int.Cl. F25B 1/00 Field of Search 62/218-221, 62/235, 333, 498, 524-527;165/174, 175

References Cited UNITED STATES PATENTS Koeniger 62/235 Nov. 18, 19752,032,286 2/1936 Kitzmiller 62/219 2,158,792 5/1939 Erbach 165/1742,265,282 12/1941 2,270,745 l/1942 2,354,497 7/1944 Brizzolara 62/219Primary ExaminerWil1iam F. ODea Assistant Examiner-Ronald C. CaposselaAttorney, Agent, or Firm-A. Yates Dowell, Jr.

57 ABSTRACT A refrigerant system in which liquid halocarbon compoundrefrigerant is delivered at pressures in excess of evaporation pressurethrough metering outlets in a supply header of an evaporator in a mannerto provide uniform cooling throughout the evaporator and utilizing areturn header and 1iquid-vapor lift apparatus to return vaporized andunevaporated refrigerant to an accumulator-separator of therefrigeration system.

8 Claims, 5 Drawing Figures US. Patent Nov. 18, 1975 DIRECT LIQUIDREFRIGERANT SUPPLY AND RETURN SYSTEM CROSS-REFERENCE TO RELATEDAPPLICATIONS This application is a countinuation-in-part of applicantsapplication Ser. No. 352,814 filed April 19, 1973 and now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention.

This invention relates generally to direct liquid refrigerant systems ofvarious kinds which may be used as the cooling means for ice rinks andthe like and relates specifically to a direct refrigerant supply andreturn system which provides a substantially uniform refrigerant flowthrough an evaporator having multiple, single pass, parallel heatexchange pipes and which includes a vaporliquid lift apparatus to enableunevaporated refrigerant to be entrained in the vaporized refrigerantand returned to an accumulator-separator of a refrigeration system.

2. Description of the Prior Art.

Heretofore many efforts have been directed to providing refrigerantsystems for use in heat exchange substructures for ice rinks. In thepast, secondary or indirect fluid systems were utilized in whichindirect cooling of a surface area was primarily accomplished by using abrine based solution as the heat exchange media which had previouslybeen cooled by a separate refrigerant system. In recent years, indirectfluid systems have become outmoded in favor of direct liquid refrigerantsystems due to the expense and inefficiencies of the indirect systems.

Direct liquid refrigerant systems have presented problems due to thedifficulty of maintaining substantially constant flow at predeterminedpressures throughout the heat exchange area of the system. An example ofstructures in the prior art is US. Pat. No. 3,466,892 to Holmsten whichdiscloses a multiple parallel pipe heat exchange system. This patentdiscloses a centrally fed supply header which supplies refrigerant fluidto a series of parallel pipes that are connected at one end to thesupply header and connected at the opposite end to a return headerhaving a central discharge pipe. This structure at ordinary rates offlow does not provide uniform refrigerant flow through the parallelpipes and thus cooling effect fluctuates as the pressure variance causesa change in the temperature gradient of the system. In order for such asystem to operate effectively, it is necessary to force the refrigerantthrough the system at greater pressures and therefore requires a greaterrefrigerant flow to obtain a more uniform evaporation rate. Further,there has been no effort to insure a steady and uniform return of theunevaporated liquid refrigerant and vapors to the accumulatorseparatorin order to reduce or prevent slugging of liquid being returned to therefrigeration system. This slugging causes variations of pressure andliquid levels in the system and subsequently these changes of theoperating conditions cause a change in the compression inlet pressureand thereby place an irregular load on the compressor and othercomponents.

Other patents, such as US. Pat. No. 3,485,057 to Etter el al. disclosesystems for use with a multiple pass floor substructure system using anammonia refrigerant. This type of system is satisfactory for use withinorganic compounds such as ammonia (Refrigerant 717), where theindividual pipes are grouped into feed circuits of two or more pipes bymeans of return bends.

SUMMARY OF THE INVENTION The present invention includes a supply andreturn system for use with a halocarbon compound or other refrigerant toprovide a direct heat exchange structure for an ice rink or the like.The system has a supply header which is flooded throughout its lengthand which supplies liquid refrigerant to multiple, parallel, single passheat exchange pipes through self-cleaning metering valves. The supplyheader feeds the heat exchange pipes in a diametric relationship to theorder in which the heat exchange pipe delivers vapor and unevaporatedliquid refrigerant to a return header, thereby providing uniform coolingthrough the heat exchange area. The system includes a stepped variablecapacity return header which maintains substantially constant pressurewithin the heat exchange pipes and cooperates with a liquid-vapor liftapparatus in such a manner as to allow unevaporated refrigerant to beentrained in the vaporized refrigerant stream and thus return theunevaporated refrigerant to an accumulator-separator of a refrigerationsystem in an uninterrupted flow with the vaporized refrigerant.

It is an object of the invention to provide a direct, single pass,multiple parallel pipe refrigerant supply and return system of a typewhich is appropriate for use as the heat exchange substructure in icerinks.

Another object of the invention is to provide a system which maintainsan even distribution of refrigerant at nearly uniform pressuresthroughout the multiple pipes of the evaporator.

It is a further object of this system to provide metering valves whichare self-cleaning and readily replaceable to insure a constant anduniform delivery of refrigerant to the evaporator from the supplyheader.

It is a further object of this invention to provide a system having aliquid-vapor lift apparatus which allows unevaporated liquid refrigerantto be raised a substantial height as an entrainment in the vapor streamand discharged into the accumulator-separator of a refrigerating systemwhile the liquid flow rate to the supply header remains relativelyconstant during compressor operation but regardless of changingcompressor capacity in response to changing load.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view of the directliquid supply and return system and schematically illustrating itsrelationship to an accumulator-separator of a refrigeration system.

FIG. 2 is an enlarged side elevation of the return header of the system.

FIG. 3 is an enlarged end view thereof.

FIG. 4 is an enlarged fragmentary section taken along the line 4-4 ofFIG. 1.

FIG. 5 is an enlarged vertical section of the vaporliquid lift assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT With continued reference to thedrawing, a refrigerant supply and return system 10 is provided having anevaporator E for use with a conventional refrigeration system 11 of anice rink or the like 12. As illustrated in FIG. 1, the conventionalrefrigeration system 11 includes a separating and delivery apparatus oraccumulator-separator 13 having a liquid control L and in whichvaporized refrigerant is separated from unevaporated liquid refrigerantreturning from the supply and return system 10. The separatedrefrigerant vapor in the accumulator-separator 13 is discharged througha suction line 14 to one or more compressors 15 which compress the vaporand discharge the same through lines 16, oil separator 17, and line 18to a condenser 19.

If desired, the compressors 15 could be provided with speed changecontrols; however, two compressors normally are provided with eachcompressor having a 50% capacity reduction. Thus, a system such as thatillustrated in FIG. 1, usually operates at 50%, 75% or 100% of itscapacity depending upon operating conditions. From the condenser theliquid refrigerant is discharged to a receiver 20 and through a line 21having an expansion control valve 22 to the accumulatorseparator 13. Theliquid level control L regulates the amount of liquid refrigerant whichis discharged from the receiver 20 into the accumulator-separator 13 sothat a substantially constant liquid level is maintained therein.

In the preferred embodiment, refrigerant 22 (Chlorodifluoromethane) isused as the direct heat exchange media. In FIG. 1, liquid refrigerant isdelivered under pressure by a pump Pfrom the accumulator-separator 13 toa supply pipe 26 having check valve C. The supply pipe 26 carries theliquid refrigerant to the receiving end or inlet 27 of supply header 28.The refrigerant feed to the supply header is substantially constant andat a rate equal to at least full capacity of the evaporator and usuallyat a greater capacity.

With reference to FIG. 4, the supply header 28 is provided with aplurality of generally upright discharge pipes 29 within each of whichis mounted a metering valve 30. Each metering valve 30 includes a body31 having a vertically disposed tapered bore 32 and a concentric taperedcounterbore 33. The tapered bore 32 is threaded for at least a portionof its length and threadedly receives a metering plug 34 having an axialorifice 35 extending entirely therethrough providing communicationbetween the discharge pipe 29 and the counterbore 33. A closure plug 36is threadedly received within the counterbore 33 to prevent the passageof refrigerant to the exterior of the body 31.

The orifice 35 is of a size to permit a predetermined quantity of liquidrefrigerant to pass therethrough at a desired pressure. In order to makecertain that the orifice 35 remains open and to make certain that thereis no buildup of material which would restrict flow therethrough, a wireinsert 37 having outwardly bent ends 38 is inserted within the orifice35 with such wire insert being slightly longer than the length of themetering plug 34. Liquid refrigerant passing through the orifice causesthe wire insert 37 to jiggle or move in a haphazard manner to keep theorifice clean of all materials. The wire insert is of a specificdiameter relative to the diameter of the orifice to permit apredetermined quantity of refrigerant to pass through the orifice. It iscontemplated that by changingthe diameter of the wire within theorifices, the flow of refrigerant can be either increased or furtherrestricted. It is apparent that the metering plug 34 can be easilyremoved from the body 31 to repair or replace the wire insert 37 or toreplace the metering plug 34 with another plug having a different sizeorifice or wire insert.

The body 31 is provided with an enlargement or boss 39 at one side andsuch boss has a bore 40 providing communication between the counterbore33 and the exterior of the body. A heat exchange pipe 41 of theevaporator E is connected to each of the metering valves 30 incommunication with the outlet bore 40 and such pipes are situated in agenerally parallel relationship and disposed generally perpendicular tothe supply header 28.

The heat exchange pipes 41 are equally spaced along the length of thesupply header at intervals determined by the effective heat exchangeareas required with a spacing of approximately four inches having beenfound satisfactory for an ice rink. Vapor and unevaporated refrigerantare discharged from the heat exchange pipes into a return or dischargeheader 42 disposed generally perpendicular to such pipes and generallyparallel to the supply header 28.

The return header is of stepped eccentric construction having sections43, 44 and 45 of progressively larger diameters respectively. Thesesections are situated along a common upper grade line 46 which runsacross the top of each of the sections 43, 44 and 45 and therefore has astepped increasing lower grade line 47 defined by the bottom of eachpipe. This configuration allows for the necessary increase in capacitywithout pressure increase as the flow is increased as each successiveheat .exchange pipe discharges into the return header. Also, the steppedlower grade line 47 permits the refrigerant to flow by gravity fromsections 43-45 while allowing the heat exchange pipes to enter thereturn header 42 at a common elevation.

Although thereturn header is described here as having three sections,any desired number could be used to achieve the same effect. Also, thelower grade line 47 could have a constant slope from end to end.

The evaporated and unevaporated refrigerant which is received by thereturn header 42 is discharged through a line 48 into a vapor-liquidlift assembly 49. The discharge line 48 is located diametricallyopposite the inlet end 27 of the supply header 28 so that all of therefrigerant flow paths are substantially equal in resistance and thepressures within the heat exchange pipes 41 are substantially constant.The lift assembly 49, FIG. 5, includes a vertically positioned elongatedgenerally cylindrical side wall 50 with a bottom wall 51 at one end anda top wall 52 at the other end forming a receptacle for vaporized andunevaporated refrigerant. The return line 48 enters the side wall at apoint below the top wall 52. A pair of vertically disposed dischargepipes 53 and 54 extend through the top wall 52 and are welded orotherwise connected thereto. The vertical discharge pipes 53 and 54 arepositioned so that their intakes 55 and 56 respectively are below thedischarge line 48. The intake 56 of the vertical discharge pipe ispositioned below the intake 55 of the discharge pipe 53 with the spacingbetween such intakes depending upon the quantity of evaporated andunevaporated refrigerant being introduced to the lift assembly 49 fromthe return header 42.

The vertical discharge pipe 53 normally is smaller in diameter than thepipe 54 and is ofa diameter such that when the compressors are operatingat minimum capacity, the suction through line 53 withdraws a mixture ofvapor having liquid entrained therein at a velocity of not less than1,000 feet per minute. Such velocity is necessary to insure that theliquid remains entrained in the evaporated refrigerant and does notcollect along the inner wall of the vertical discharge pipe and run backinto the lift assembly.

When the compressors are operating at minimum capacity, the liquid levelin the lift assembly is relatively high and the flow of the liquid-vapormixture is entirely through the upper discharge line 53 since thesuction is not sufficient to withdraw liquid through line 54. As thecapacity of thecompressor is increased to meet the load demands whichcause increased vaporization in the heat exchange pipes the volume offlow in lines 53 and 54 increases.

At a predetermined compressor capacity, flow through pipe 54 isinitiated and a momentary slug of liquid may be discharged therethroughdepending upon the relative elevated spacing between inlets 55 and 56 ofpipes 53 and 54, respectively. At maximum compressor capacity, theliquid level in the vapor-liquid lift is such that the flow of theliquid-vapor mixture passes through both pipes 53 and 54. In someinstances, it may be advantageous to use three or more verticaldischarge pipes situated at various levels in the lift assembly.

The purpose of the lift assembly 49 is to raise excess liquid which isnot evaporated, with a minimum of pressure penalty, from the rink floorlevel into the accumulator-separator which usually is much higherbecause of the structure of the building. Therefore, it is necessary toprovide a velocity of flow in one or more of the vertical pipes 53 and54 under any of the several capacity steps of the compressors such thatthe velocity in any vertical pipe is not less than 1,000 feet per minutethus providing a vertical movement of unevaporated liquid as anentrainment in the vapor stream. As an example, if the volume of liquidrefrigerant delivered to the supply header is 1.5 times greater thanevaporation, then at full load, the weight of the unevaporated liquid isequal to approximately 50% of the weight of the vapor, but the volume ofthe liquid is very small when compared to the vapor volume. Theunevaporated liquid refrigerant returned to the accumulator-separator isinversely proportional to the load on the evaporator but is readilymoved with the vapor, providing vapor velocity is never less than 1,000feet per minute.

In the operation of the device, liquid refrigerant is pumped at aconstant volume from the accumulatorseparator to the supply header 28under all load conditions. From the supply header the liquid refrigerantis fed to the plurality of heat exchange pipes 41 through the meteringvalves 30. The orifice 35 of each metering valve and the wire inserttherethrough permit a specific quantity of liquid to be fed to each heatexchange pipe at a desired pressure. The wire insert 37, being free tomove with the orifice, also functions to prevent the buildup of anymaterial which would tend to restrict the flow through the valves.

Under normal operating conditions, a portion of the liquid refrigerantundergoes a change of state in the heat exchange pipe 41 as heat energyis absorbed from the ice rink or the like 12. Subsequently, bothevaporated and unevaporated refrigerant are discharged into the returnheader 42.

The progressively larger diameters of the stepped eccentric returnheader allows for the necessary increase in capacity without pressureincrease as the flow increases due to the discharge from successive heatexchange pipes.

The unevaporated and evaporated reflgerant is discharged from the returnheader into the vapor-liquid lift apparatus 49. The discharge from thereturn header is located diametrically opposite the inlet to the supplyheader so that refrigerant flow paths through the headers and each heatexchange pipe are substantially equal, thereby aiding in maintaining amore uniform heat exchange rate in the evaporator.

The refrigerant discharged into the vapor-liquid lift apparatus isreturned through discharge lines 54 and/or 53, in which suction iscreated by the compressors 15, to the accumulator-separator as a mixtureof unevaporated refrigerant entrained in evaportated refrigerant.

Systems of the type described herein usually have two compressors eachof which will have 50% capacity reduction, thus a minimum capacity is 5of the total capacity and the system may be operated at 1, A, and fullcapacity by controls responsive to operating pressure. The pressuredifferential necessary to generate a desired velocity in the verticallift pipes is directly proportional to compressor pumping capacity.Thus, at minimum capacity, the liquid level in the lift assembly isrelatively high and the vapor with unevaporated liquid refrigerantentrained therein is raised entirely through the upper suction orvertical line 53 at a rate of at least 1,000 feet per minute. Atcapacity, the velocity in the vertical line 53 is increased and theliquid level is lowered, but not sufficient to uncover the vertical line54. At substantially capacity, the vertical line 54 is uncovered andvapor and unevaporated refrigerant flows vertically through both lines53 and 54 but the sizes have been proportioned so that the velocity ineach line is not less than 1,000 feet per minute. At full capacity theliquid level is further lowered because of the increased flow in both ofthe vertical pipes.

We claim:

1. A direct liquid refrigerant supply and return apparatus including anevaporator for use with a refrigeration system having anaccumulator-separator, said apparatus comprising a supply header havingan inlet at one end for receiving pressurized liquid refrigerant fromthe accumulator-separator, a plurality of heat exchange pipes locatedsubstantially parallel with each other and generally perpendicular tothe supply header, each of said heat exchange pipes being connected atone end to said supply header, a return header in spaced generallyparallel relationship to said supply header, the opposite end of each ofsaid heat exchange pipes communicating with said return header, saidreturn header having discharge means at one end for dischargingvaporized and unevaporated refrigerant therefrom, said discharge meansbeing diametrically opposite said inlet to said supply header so thatthe refrigerant flow paths from the inlet of said supply header throughsaid heat exchange pipes and said return header are substantially ofequal resistance, a vaporliquid lift apparatus including a receptaclefor receiving vaporized and unevaporated refrigerant from the dischargemeans of said return header, at least one discharge pipe having one endextending into said receptacle and the other end communicating with theaccumulator-separator, the unevaporated refrigerant being entrained inthe vaporized refrigerant within said receptacle, and means for movingthe vaporized refrigerant and the unevaporated refrigerant entrainedtherein to the accumulator-separator at a velocity to maintain theentrainment of the unevaporated refrigerant.

2. The structure of claim 1 including a plurality of metering meanscarried by said supply header, each of said metering means having a bodywith a bore and a counterbore concentric with said bore, plug meanshaving a metering orifice removably mounted in said bore, said bodyhaving inlet means providing communication between said supply headerand said orifice and oulet means providing communication between saidcounterbore and said heat exchange pipes, and closure means removablymounted in said counterbore, whereby said plug means may be selectivelyremoved from said body when said closure means is removed from saidcounterbore.

3. The structure of claim 2 including an insert mounted in said meteringorifice and being freely movable therein to prevent clogging of saidorifice.

4. The structure of claim 1 wherein said return header includes aplurality of sections of progressively increasing diameterseccentrically connected together along a common substantially horizontalupper grade line and a stepped lower grade line, said discharge meansbeing adjacent the larger end of said return header.

5. The structure of claim 1 in which said receptacle includes avertically disposed generally cylindrical side wall having a top walland a bottom wall fixed thereto.

6. The structure of claim 1 including a plurality of discharge pipeshaving ends terminating at different elevations within said receptacleto provide for varying capacities of flow to the accumulator-separator.

7. The structure of claim 6 in which said discharge pipes are ofdifferent diameter.

8. The structure of claim 6 in which the pipe for minimum capacity hasthe least extension into said receptacle and each additional pipe forincreased capacity extends further into said receptacle.

1. A direct liquid refrigerant supply and return apparatus including anevaporator for use with a refrigeration system having anaccumulator-separator, said apparatus comprising a supply header havingan inlet at one end for receiving pressurized liquid refrigerant fromthe accumulator-separator, a plurality of heat exchange pipes locatedsubstantially parallel with each other and generally perpendicular tothe supply header, each of said heat exchange pipes being connected atone end to said supply header, a return header in spaced generallyparallel relationship to said supply header, the opposite end of each ofsaid heat exchange pipes communicating with said return header, saidreturn header having discharge means at one end for dischargingvaporized and unevaporated refrigerant therefrom, said discharge meansbeing diametrically opposite said inlet to said supply header so thatthe refrigerant flow paths from the inlet of said supply header throughsaid heat exchange pipes and said return header are substantially ofequal resistance, a vapor-liquid lift apparatus including a receptaclefor receiving vaporized and unevaporated refrigerant from the dischargemeans of said return header, at least one discharge pipe having one endextending into said receptacle and the other end communicating with theaccumulator-separator, the unevaporated refrigerant being entrained inthe vaporized refrigerant within said receptacle, and means for movingthe vaporized refrigerant and the unevaporated refrigerant entrainedtherein to the accumulator-separator at a velocity to maintain theentrainment of the unevaporated refrigerant.
 2. The structure of claim 1including a plurality of metering means carried by said supply header,each of said metering means having a body with a bore and a counterboreconcentric with said bore, plug means having a metering orificeremovably mounted in said bore, said body having inlet means providingcommunication between said supply header and said orifice and ouletmeans providing communication between said counterbore and said heatexchange pipes, and closure means removably mounted in said counterbore,whereby said plug means may be selectively removed from said body whensaid closure means is removed from said counterbore.
 3. The structure ofclaim 2 including an insert mounted in said metering orifice and beingfreely movable therein to prevent clogging of said orifice.
 4. Thestructure of claim 1 wherein said return header includes a plurality ofsections of progressively increasing diameters eccentrically connectedtogether along a common substantially horizontal upper grade line and astepped lower grade line, said discharge means being adjacent the largerend of said return header.
 5. The structure of claim 1 in which saidreceptacle includes a vertically disposed generally cylindrical sidewall having a top wall and a bottom wall fixed thereto.
 6. The structureof claim 1 including a plurality of discharge pipes having endsterminating at different elevations within said receptacle to providefor varying capacities of flow to the accumulator-separator.
 7. Thestructure of claim 6 in which said discharge pipes are of differentdiameter.
 8. The structure of claim 6 in which the pipe for minimumcapacity has the least extension into said receptacle and eachadditional pipe for increased capacity extends further into saidreceptacle.